. Introduction
Rubber latex is an aqueous dispersion of natural rubber particles, produced from natural rubber trees (Hevea brasiliensis). The rubber particles in fresh natural rubber latex consists of a rubber hydrocarbon core (polyisoprene) surrounded by a shell of protein (mainly α-globulin) and phospholipid (mainly lecithin) which are intimately mixed together over the particle surface [1]. In industry, ammonia is added to the rubber particle dispersion (latex) in order to increase the pH from 6.5 to 10.5. This pH is well above the isoelectric point of the protein (pH ≈ 4), thus increasing negative charges on the surface. In addition, the lecithin becomes hydrolyzed producing long chain fatty acid anions. As a consequence, the addition of ammonia causes a significant enhancement of the latex stability against particle aggregation due to the increase in the zeta potential, which gives a high electrostatic barrier that becomes sufficient for stabilization of the latex [2], [3], [4], [5], [6] and [7]. Moreover, the protein molecules become unfolded forming a strongly hydrated layer thus producing steric repulsion. One may consider the overall stability of the latex to be electrosteric in nature. The latex is then concentrated by centrifugation followed by vulcanization using sulphur in the presence of an accelerator dispersion to enhance the crosslinking process, which produces sulphur bonds [8]. This vulcanized rubber latex is used for the manufacture of both examination and surgical gloves. In order to concentrate the latex by centrifugation, it is essential to enhance the stability of the rubber particles against aggregation during the centrifugation process. This is achieved by addition of various surfactants such as potassium oleate, potassium laurate or caprylate or sodium dodecyl sulphate [8].